A closed terrarium is a tiny garden that looks after itself. Inside the sealed glass, water evaporates from the soil and leaves, collects on the glass and trickles back down, so the plants keep recycling the same moisture for weeks at a time. Get a few basics right – light, water and air – and a closed terrarium can stay green and healthy for years with only a few minutes of care a month.
Quick care summary: bright but indirect light, no direct sun · water only when the glass stays completely dry for several days · open the lid for a few hours if the glass stays heavily fogged · keep it between about 18°C and 27°C · trim anything that touches the glass.
How a closed terrarium works
The lid is what makes a closed terrarium different from a plant pot. During the day, light warms the jar and moisture rises from the soil and leaves. It condenses on the cooler glass – the misty look you often see in the morning – and runs back into the soil. Because so little water escapes, a closed terrarium needs far less watering than a normal plant, and over-watering is the most common way people harm one.
1. Light: bright, but never direct sun
Place your terrarium where it gets plenty of bright, indirect light – near a window that does not get direct sunshine, or a metre or two back from a sunny one. Direct sun through glass heats a closed jar very quickly and can cook the plants inside in a single afternoon, especially in Pakistani summers.
- Good spots: a bright living room shelf, a desk near (not in) a window, a well-lit lounge or office.
- Avoid: a sunny windowsill, a balcony, or the top of a fridge or TV where it gets warm.
- If your room is dim, a regular LED lamp for 8–10 hours a day works well.
- Turn the jar a quarter turn every week or two so the plants grow evenly instead of leaning towards the light.
2. Watering: less than you think
Read the glass, not the calendar. Condensation is your watering gauge:
| What you see | What it means | What to do |
|---|---|---|
| Light mist in the morning that clears by afternoon | Healthy balance | Nothing – leave it alone |
| Heavy fog all day, drops running down the glass | Too wet | Open the lid for a few hours (or a day) to let it breathe, then close again |
| Glass completely dry for several days, soil looks pale | Too dry | Add a few sprays or one or two teaspoons of water around the edges, then close the lid |
When you do water, add a little at a time – you can always add more, but you cannot easily take it out. Many closed terrariums need water only every few weeks or even every couple of months.
Which water to use: tap water in many cities is hard and can leave white marks on the glass and build up in the soil. Filtered water, or tap water that has been boiled and cooled, is a better choice.
3. Temperature and placement
Most terrarium plants are happiest at normal room temperature, roughly 18–27°C. Keep the jar away from heaters, direct air-conditioner blasts and hot kitchens. In Rawalpindi and Islamabad summers, choose the coolest bright room in the house; in winter, keep it away from cold window glass at night.
4. Air: let it breathe when needed
A closed terrarium does not need to be opened regularly, but opening the lid for a few hours once a month – or whenever the glass stays heavily fogged – lets fresh air in and stops excess moisture building up.
5. Trimming and tidying
- Trim leaves that press against the glass – wet leaves touching glass are the first to rot.
- Remove yellow, brown or fallen leaves straight away with long tweezers or chopsticks; decaying leaves are what mould feeds on.
- If one plant is growing much faster than the rest, pinch back its tips to keep the little landscape in balance.
6. Dealing with mould
A small patch of white, fuzzy mould usually means the terrarium is too wet or something is decaying inside. Lift the mould and any rotting leaf out with a cotton bud or tweezers, leave the lid off for a day to dry the air, then close it again. If mould keeps coming back, water less and give it more indirect light.
7. Cleaning the glass
Wipe the outside with a soft, dry microfibre cloth. For the inside, use a clean cloth or cotton pad lightly dampened with plain water. Never use glass cleaner or soap – the chemicals stay inside the closed jar with your plants.
8. Feeding
Closed terrariums are designed to grow slowly, so they need little or no fertiliser. Feeding makes plants outgrow the jar quickly. If plants look pale after many months, a very weak, diluted dose once or twice a year is the most they need.
Common problems at a glance
| Problem | Likely cause | Fix |
|---|---|---|
| Leaves turning yellow and soft | Too much water | Open the lid to dry out; remove damaged leaves |
| Leaves crisp or brown at the edges | Too dry or too much heat/sun | Add a little water; move away from sun and heat |
| Plants stretching and leggy | Not enough light | Move to a brighter spot (still no direct sun) |
| White fuzzy patches | Excess moisture or decaying leaves | Remove mould and dead leaves; air out for a day |
| Glass never clears | Too much water inside | Leave the lid open for a day or two |
Frequently asked questions
How often should I water a closed terrarium?
Only when the glass has stayed dry for several days and the soil looks pale – often every few weeks to every couple of months. A healthy closed terrarium shows light condensation for part of the day.
Can I keep a closed terrarium in sunlight?
Not in direct sunlight. Sun through glass overheats a sealed jar quickly. Bright, indirect light is ideal.
Should I ever open the lid?
Yes – briefly. Open it for a few hours when the glass stays heavily fogged, or about once a month to refresh the air.
Can succulents and cacti go in a closed terrarium?
Yes – many of our terrariums include them. Succulents and cacti like drier conditions than moss and fittonia, so give them bright light, water very sparingly (around the moss, not on the cactus), and open the lid regularly to let extra moisture out. Our succulent and cactus care guide has more tips.
How long does a closed terrarium last?
With the right light and careful watering, a closed terrarium can thrive for years. Occasional trimming keeps it looking fresh.
Bring a little green world home
Every Mystical Hub terrarium is put together by hand and arrives ready to enjoy. Explore our terrariums, including the Closed Terrarium in a clear jar with lid. Terrariums are delivered in Rawalpindi & Islamabad, with Cash on Delivery. Questions about your terrarium? Message us on WhatsApp 0321-5011787 – we are always happy to help.
1 Comment